Press tools

ABSTRACT

A press tool for compacting a mass of powder into a component having a helical formation, for example a helical gear, comprises a die member shaped to produce the helical formation and a punch member complementary to the die member. The punch member is arranged to enter the die member so as to compact powder within the die member during relative axial movement between the member. One of the members, for example the punch member, is mounted by a helical bearing system having a lead equivalent to that of the helical formation. In this manner the said one member is rotated during axial movement so that the helical formation thereof follows the helical formation of the other member.

[451 Oct. 22, 1974 1 PRESS TOOLS [75] Inventor: John G. Fowler, Hayes, England [73] Assignee: Metal Compacting Tools, Ltd.,

Primary Examiner-J. Howard Flint, Jr.

Attorney, Agent, or FirmMason, Mason & Albright Hayes, England June 28, 1973 [57 ABSTRACT A press tool for compacting a mass of powder into a [22] Filed:

[211 App! 374797 component having a helical formation, for example a helical gear, comprises a die member shaped to produce the helical formation and a punch member com- [30] Foreign Application Priority Data June 29, 1972 Great Britain........,........... 30371 72 Plememary to the die member- The Punch member is arranged to enter the die member so as to compact 52 us. 425/78, 425/352 Powder within the die member during relative axial 5 lnL (1m 33% 11/04, g 3/00, 329d 15/00 movement between the member. One of the members, 581 Field of 425/78, 352 for example the Punch member, is mounted by a helical bearing system having a lead equivalent to that of the helical formation. In this manner the said one [56] References Cited UNITED STATES PATENTS member is rotated during axial movement so that the helical formation thereof follows the helical formation of the other member.

425/78 425/78 Harrington.......... 425/78 13 Claims, 2 Drawing Figures 2,561.735 7/1951 3 394 412 7/1968 Laurent 3,677,672 7/1972 wwaw m mass TOOLS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to press tools for compacting a mass of powder, and more particularly to press tools for compacting a mass of metallic powder into a component having a helical formation.

2 Description of the Prior Art.

It has been proposed to compact a mass of powder into the form of a helical gear using a punch and die of appropriate shape, the compacted mass subsequently being sintered. During the compacting operation, the punch is moved helically within the die so that the helical formation on the punch follows that on the die. If such helical movement is caused only by the interference between the helical formations on the punch and die, these components will wear rapidly, and it has therefore been proposed to positively rotate the punch during axial movement of the punch relative to the die. In one previously proposed arrangement, the punch is rotated by a complex cam/linkage system; however, the complexity of this previously proposed system is such that it cannot be used with press tools operated by me chanical presses due to the high speed of operation of such presses.

SUMMARY OF THE INVENTION According to the present invention, there is provided a press tool for compacting a mass of powder into a component having a helical formation, said tool comprising a die member shaped to produce the helical formation and arranged to receive a said mass of powder, and a punch member complementary to the die member and arranged to compact the powder within the die member upon relative axial movement between the punch member and the die member, one of said members being mounted by a helical bearing system having a lead equivalent to that of the said helical formation whereby the said one member is rotated during axial movement of the said one member relative to the other member so that the helical formation of the said one member is caused to follow the helical formation of the other member.

Further according to the present invention, there is provided a press tool for compacting a mass of metallic powder into a component having a helical formation, said assembly comprising a die member shaped to produce the helical formation and having open upper and lower ends, a first punch member having a shape complementary to that of the die member and arranged to extend into the die member through the lower end thereof, a first helical bearing system mounting one of the members for helical movement relative to the other member, the said bearing system comprising a helical track having a lead equivalent to that of the helical formation and roller means received in the track such that the said one member is moved to follow the helical formation of the other member upon relative axial move-' ment between the members.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a longitudinal section of a press tool in accordance with the present invention; and

FIG. 2 shows schematically a recirculating bearing system for a lower punch of the press tool.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings, a press tool for compacting a mass of metallic powder into the form of a helical gear comprises a stationary die block 2 which supports an annular die-mounting insert 4 recessed into the upper surface of the die block 2. A die 6 in the form of a bush is mounted within the inner surface of the insert 4 and defines a die cavity shaped to the profile of the gear to be formed. The die cavity is open at its upper and lower ends to receive upper and lower punches 8 and 10, the end portions 8' and I0 of which have a profile complementary to that of the die cavity.

The lower punch 10 is reciprocable relative to the die block 2 and extends upwardly from a mounting block 12 and through a bore in the die block 2 to enter the die cavity from below. The punch 10 is supported for rotation in the mounting block 12 through thrust bearings 14 and is mounted in the die block by means of a helical recirculatory bearing system 16 which causes the punch 10 to rotate when reciprocated relative to the die block 2.

The bearing system 16 comprises a sleeve 18 surrounding a portion of the punch 10, the outer surface of the sleeve 18 being formed with a number of helical tracks 20 having a lead equivalent to that of the helical profile of the punch. The sleeve 18 is surrounded by a stationary bushing 22 mounted within a cylindrical recess in a bearing block 23 mounted on the underside of the die block 2. Helical tracks 24 of complementary profile to the tracks 20 are formed on the inner surface of the bushing 22 and helical tracks 26 are formed on the outer surface of the bushing 22. Each track 26 is associated with one of the tracks 24, and radial grooves are formed in the axial end faces of the bushing 22 to form tracks 28 which connect the associated tracks 24, 26 at their upper and lower ends. Roller means in the form of balls are interposed between the tracks 20 and 24 and are freely movable along the tracks; the balls upon reaching one end of the tracks 20, 24 during movement of the punch 10, pass via the adjacent track 28 into the associated track 26 and move along to track 26 to be returned to the other end of the tracks 20, 24 via the adjacent track 28.

Preferably, the tracks 20, 24 are in the form of triangular section grooves, and the tracks 26 and 28 are in the form of rectangular section grooves.

In order to form a bore or other axial aperture through the finished helical gear, a core rod 32 extends coaxially into the die cavity through an axial passage in the lower punch 10. The core rod v32 extends upwardly from a stationary mounting member 34 located in a cylindrical cavity in the mounting block 12 and secured against reciprocation with the punch 10. Preferably, the core rod is carried from the mounting member 34 by means of a bearing (for example a plain bearing 36) so as to be freely rotatable relative to the die block 2.

The upper punch 8 is arranged to enter the die cavity from above and is mounted in a stepped axial bore in an upper mounting block 38; the punch 8 is supported for rotation in the mounting block 38 by means of a thrust bearing 40. An annular bearing block 42 reciprocable in the stepped bore is concentric with the upper punch 8 and engages the upper punch 8 through a helical bearing system 43. The helical bearing system 43 comprises a sleeve 44 surrounding a portion of the punch 8 and having a number of helical tracks 46 similar to the tracks and having a lead equivalent to that of the helical profile of the upper punch 8. A stationary bushing 48 which surrounds the sleeve 44, is secured within the bearing block 42 and has helical tracks 50 on its inner surface, the tracks 50 being complementary with the tracks 46. Roller means in the form of balls are interposed between the tracks 46, 50. If the stroke of the bearing block 42 in the stepped bore is sufficient, the bearing system 43 can be a recirculatory system identical to the bearing system 16 for the lower punch.

The bearing block 42 is biased downwardly in the stepped bore by means of compressed air or other fluid fed via a port 52 into an annular chamber 54 defined between the stepped surface of the bore and the bearing block 42. Alternatively, the bias can be provided by springs interposed between a step in the surface of the bore and the bearing block 42.

The upper punch 8 extends downwardly through the bearing block 42 and a foot member 56 extends downwardly from the under-surface of the bearing block 42 to a level below the bottom end of the punch 8. An axial passage is provided through the punch 8 to enable it to mate with the core rod 32 when the upper punch 8 is located in the die cavity. If the core rod 32 is of square or other non-circular section, a sleeve 58, having an internal section complementary to that of the core rod 32, is rotatably mounted in the axial passage to receive the core rod 32. A head 58 at the upper end of the sleeve 58 engages a thrust bearing 60 mounted in the mounting block 38. The sleeve 58 is angularly biased by means of helical spring 62 into a stop position in which the sleeve 58 is aligned with the core rod 32 when the upper punch 8 enters the die cavity, the spring 62 lying between the head 58' of the sleeve 58, and the thrust bearing 60.

In use, the upper and lower punches 8, 10 are mounted, by means of their respective mounting blocks 38, 12 on the opposed platens of a press and the lower punch 10 is positioned to close the lower end of the die cavity. Metallic powder is then charged into the die cavity from a hopper (not shown), which traverses the upper surface of the die block 2. When the die cavity has been charged with the appropriate quantity of powder, the upper punch 8 is moved downwardly towards the die cavity. Shortly before the upper punch 8 enters the die cavity, the foot member 56 contacts the insert 4 thus displacing the bearing block 42 upwardly relative to the upper punch 8 and to the upper mounting block 38, this relative displacement causes, by means of the helical bearing system 43, rotation of the upper punch 8. Thus, when the upper punch 8 enters the die cavity to compact the powder, it is rotating by the required amount to follow the helical profile of the die cavity, rotation of the punch 8 continuing while the punch 8 moves downwardly in the die cavity.

When the powder has been compacted to the required degree, the upper punch 8 is withdrawn from the die cavity, the punch 8 being rotated in the reverse sense during withdrawal by means of the helical bearing system 43.

After withdrawal of the upper punch 8, the lower punch 10 is displaced upwardly by means of its mounting block 12 to eject the compacted mass from the die cavity. Likewise, by means of the helical bearing system 16, the lower punch 10 is rotated relative to the die block 2 so as to follow the helical profile within the die cavity. During this movement, the core rod 32 will tend to rotate with the compacted mass while the mass is being ejected from the die cavity; in this manner, the mass is moved purely linearly along the core rod 32, as will be necessary if the core rod has a square, a keyed, or other non-circular profile.

When the compacted mass has been ejected from the die cavity, the lower punch 10 is moved downwardly and the foregoing cycle is repeated. After ejection, the compacted mass is sintered in known manner.

The press tool described is particularly suitable for use on a mechanical press since the tool has relatively few moving parts and can operate at such speeds as are likely to be encountered in mechanical presses.

Although in the tool particularly described the upper punch is moved downwardly into a stationary die cavity and the punches are rotated, such relative movement can alternatively be provided by moving the die block upwardly towards the upper punch and/or by rotating the die block.

What is claimed is:

l. A press tool for compacting a mass of powder into a component having a helical formation, said tool comprising a die member having a helical formation and arranged to receive a said mass of powder,

a punch member having a helical formation complementary to that of the die member and arranged to compact the powder within the die member upon relative axial movement between the punch member and the die member,

a helical bearing system mounting one of said members, said helical bearing system having a lead equivalent to that of the said helical formation whereby the said one member is rotated during axial movement of the said one member relative to the other member so that the helical formation of the said one member is caused to follow the helical formation of the other member, and

a member mounting the said one member, and

wherein the helical bearing system comprises a plurality of helical tracks carried by the said one member,

a plurality of tracks carried by the mounting member, each track carried by the mounting member being associated with a respective track carried by the said one member, and

balls interposed between the associated tracks.

2. A press tool as claimed in claim 1, wherein the bearing system is a recirculatory system.

3. A press tool as claimed in claim 1, further comprismg a freely rotatable core rod extending into the die.

4. A press tool for compacting a mass of metallic powder into a component having a helical formation, said assembly comprising a die member having a helical formation and open upper and lower ends,

a first punch member having a helical formation complementary to that of the die member and arranged to extend into the die member through the lower end thereof, and

a first helical bearing system mounting one of the members for helical movement relative to the other member, the said bearing system comprising a helical track having a lead equivalent to that of the helical formation and a plurality of unmounted roller means movably and operatively received in the track such that the said one member is moved to follow the helical formation of the other member upon relative axial movement between the members.

5. A press tool as claimed in claim 4, further comprisa second punch member having a shape complementary to that of the die member and arranged to extend into the die member through the upper end thereof,

a mounting member,

a second helical bearing system supporting the second punch member from the mounting member, said second helical bearing system comprising a track having a lead equivalent to that of the helical formation, and

a plurality of unmounted roller means movably and operatively received in the track such that the second punch member is moved to follow the helical formation of the die member during relative axial movement between the second punch member and the die member.

6. A press tool as claimed in claim 5, wherein the first helical bearing system comprises co-operating helical tracks rigid with the die member and the first punch member respectively, and

roller means in the form of balls interposed between the tracks.

7. A press tool as claimed in claim 6, wherein the first helical bearing system further comprises a track extending between the ends of the cooperating helical tracks whereby to return to one end of the co-operating tracks, balls discharged from the other end of the co-operating tracks.

8. A press tool as claimed in claim 5, wherein the second helical bearing system comprises CO-operating helical tracks rigid with the mounting member and the second punch respectively, and

roller means in the form of balls interposed between the tracks.

9. A press tool as claimed in claim 5, wherein the die member is fixed and the first and second punch members are reciprocable relative to the die member.

10. A press tool as claimed in claim 5, wherein the die member is shaped to produce a said component in the form of a helical gear.

11. A press tool as claimed in claim 5, wherein the first punch member is tubular, said tool further comprising a freely rotatable core rod extending axiallyinto the die member through the first punch member, the first punch member being reciprocable relative to the core rod.

12. A press tool as claimed in claim 6, wherein the first and second punch members are tubular, said tool further comprising a freely rotatable core rod extending axially into the die member through the first punch member, the first punch member being reciprocable relative to the core rod a sleeve having an internal cross-section corresponding to the external cross-section of the core rod, said sleeve being rotatably mounted within the second punch member and receiving the core rod when the second punch member is located within the die member.

13. A press tool for compacting a mass of metallic powder into a component having a helical formation, said tool comprising a die member having -a helical formation and upper and lower ends,

a first punch member having a helical formation complementary to that of the die member and arranged to extend into the die member through the lower end thereof, and

a first helical bearing system mounting one of said members for helical movement relative to the other said member, said bearing system comprising a first helical track having a lead equivalent to that of the helical formation rigidly connected to one said member,

a second helical track also having a lead equivalent to that of the helical formation rigidly connected to the other said member, and

unmounted roller means at all times movably and operably received in both said first and said second tracks whereby said one member is moved to follow the helical formation of the other said member upon relative axial movement between said members, and said first and said second tracks are maintained by said roller means at all times in juxtaposition in at least a portion of each of said tracks. 

1. A press tool for compacting a mass of powder into a component having a helical formation, said tool comprising a die member having a helical formation and arranged to receive a said mass of powder, a punch member having a helical formation complementary to that of the die member and arranged to compact the powder within the die member upon relative axial movement between the punch member and the die member, a helical bearing system mounting one of said members, said helical bearing system having a lead equivalent to that of the said helical formation whereby the said one member is rotated during axial movement of the said one member relative to the other member so that the helical formation of the said one member is caused to follow the helical formation of the other member, and a member mounting the said one member, and wherein the helical bearing system comprises a plurality of helical tracks carried by the said one member, a plurality of tracks carried by the mounting member, each track carried by the mounting member being associated with a respective track carried by the said one member, and balls interposed between the associated tracks.
 2. A press tool as claimed in claim 1, wherein the bearing system is a recirculatory system.
 3. A press tool as claimed in claim 1, further comprising a freely rotatable core rod extending into the die.
 4. A press tool for compacting a mass of metallic powder into a component having a helical formation, said assembly comprising a die member having a helical formation and open upper and lower ends, a first punch member having a helical formation complementary to that of the die member and arranged to extend into the die member through the lower end thereof, and a first helical bearing system mounting one of the members for helical movement relative to the other member, the said bearing system comprising a helical track having a lead equivalent to that of the helical formation and a plurality of unmounted roller means movably and operatively received in the track such that the said one member is moved to follow the helical formation of the other member upon relative axial movement between the members.
 5. A press tool as claimed in claim 4, further comprising a second punch member having a shape complementary to that of the die member and arranged to extend into the die member through the upper end thereof, a mounting member, a second helical bearing system supporting the second punch member from the mounting member, said second helical bearing system comprising a track having a lead equivalent to that of the helical formation, and a plurality of unmounted roller means movably and operatively received in the track such that the second punch member is moved to follow the helical formation of the die member during relative axial movement between the second punch member and the die member.
 6. A press tool as claimed in claim 5, wherein the first helical bearing system comprises co-operating helical tracks rigid with the die member and the first punch member respectively, and roller means in the form of balls interposed between the tracks.
 7. A press tool as claimed in claim 6, wherein the first helical bearing system further comprises a track extending between the ends of the cooperating helical tracks whereby to return to one end of the co-operating tracks, balls discharged from the other end of the co-operating tracks.
 8. A press tool as claimed in claim 5, wherein the second helical bearing system comprises CO-operating helical tracks rigid with the mounting member and the second punch respectively, and roller means in the form of balls interposed between the tracks.
 9. A press tool as claimed in claim 5, wherein the die member is fixed and the first and second punch members are reciprocable relative to the die member.
 10. A press tool as claimed in claim 5, wherein the die member is shaped to produce a said component in the form of a helical gear.
 11. A press tool as claimed in claim 5, wherein the first punch member is tubular, said tool further comprising a freely rotatable core rod extending axially into the die member through the first punch member, the first punch member being reciprocable relative to the core rod.
 12. A press tool as claimed in claim 6, wherein the first and second punch members are tubular, said tool further comprising a freely rotatable core rod extending axially into the die member through the first punch member, the first punch member being reciprocable relative to the core rod a sleeve having an internal cross-section corresponding to the external cross-section of the core rod, said sleeve being rotatably mounted within the second punch member and receiving the core rod when the second punch member is located within the die member.
 13. A press tool for compacting a mass of metallic powder into a component having a helical formation, said tool comprising a die member having a helical formation and upper and lower ends, a first punch member having a helical formation complementary to that of the die member and arranged to extend into the die member through the lower end thereof, and a first helical bearing system mounting one of said members for helical movement relative to the other said member, said bearing system comprising a first helical track having a lead equivalent to that of the helical formation rigidly connected to one said member, a second helical track also having a lead equivalent to that of the helical formation rigidly connected to the other said member, and unmounted roller means at all times movably and operably received in both said first and said second tracks whereby said one member is moved to follow the helical formation of the other said member upon relative axial movement between said members, and said first and said second tracks are maintained by said roller means at all times in juxtaposition in at least a portion of each of said tracks. 